I don't know what you need answering, but go for it, before prices go up because of low stock.
Here is a excellent post : http://forums.nvidia.com/index.php?showtopic=158727
You can use a 2nd card in certain situations just for AA
I use it for ultimate IQ in games that don't need all the power of 2 cards. But lets me unload the AA hit from the main card, resulting in higher than single card performance. With AA cranked.
SLI ANTI-ALIASING (SLI AA)
SLI anti-aliasing is a rendering mode that enhances image quality rather than performance by dividing the specified sampling rate among an even number of processors. The utilized GPUs will all draw the exact same frame but perform pixel sampling slightly differently on each GPU through the use of coverage offsets. The sampled frame is sent to the successive GPU and merged with its sampled frame; in 2-way SLI systems, the slave GPU sends its frame to the primary; in 4-way SLI, the fourth GPU will send its frame to the third GPU to be blended with its, which will then send that frame to the second GPU for blending, then finally that frame is submitted to the primary GPU where it is blended once more and then displayed on the monitor. This staggered blending approach evenly distributes the computational strains among the processors so the primary GPU isn't overwhelmed in having to blend all four frames by itself. Unfortunately for 3-way SLI users, no anti-aliasing rates exist that permit even distribution across three GPUs, meaning that the secondary slave GPU will not be used for rendering when SLI AA is in use. This option is found in the "Antialiasing - Mode" drop-down menu of the NVIDIA Control Panel for global and application-specific profiles and will automatically override the set SLI rendering mode if selected.
Crowe, the avg user will never notice the difference in their electric bill. Lets be realistic.